The present invention relates to agricultural balers and, more particularly, to a baler for forming rectangular bales having a bale knotting system using twine to bind the bales.
Rectangular bales conventionally are able to maintain their shape by means of a series of parallel extending twine loops, provided lengthways around the bales. Agricultural balers, utilizing automatic knotters by which two conventional knots are made on every loop for binding a bale, have been available for many years. U.S. Pat. No. 4,142,746, for example, discloses a tying mechanism of the conventional double knotter type. Such a tying mechanism is a complex gathering of elements such as a bill hook for forming the knot, a holder in combination with a retainer for retaining the strands when forming the knot and an arm with an integrated cutter for stripping the formed knot from the bill hook in combination with the separation of the knot from the retained strands. When a bale reaches its desired length, a knot tying cycle is initiated. During this tying cycle, two knots are formed, the first knot for closing the loop of the finished bale and the second knot for starting the loop for the next bale.
In use, such conventional knotters, while being effective in binding bales with twine, result in small pieces of twine, commonly known as twine tails, being wasted after each knotting operation. These twine tails are obtained after the second knot is formed and stripped of the bill hook by a moving stripper arm. In conventional knotters, a stripper arm with an integrated cutter is used to strip the knot from the billhook. At the same time, the cutter will cut the strands that are retained by the holder. In contrast with the forming of the second knot, no twine tails will be obtained when forming the first knot, since the strands are at that point still retained by the holder and needed for forming the second knot. The first knot is merely cut loose from the strands and dropped onto the finished bale.
Although the amount of twine wasted is not great, as the twine tails are approximately only 3 to 5 cm long, they may build up in the vicinity of the knotter and ultimately cause knotter-tying problems. In some situations the twine tails are removed from the baler when the formed bale is pushed out of the baler, then the twine tails drop on the field where they may cause or contribute to environmental pollution. Indeed, nowadays farmers often use synthetic twine instead of natural fibers. Unlike natural fibers, synthetic twine will not be broken down by atmospheric influences, and therefore, the synthetic twine tails remains longer on the field and may be picked up the next harvesting season by a baler. Eventually, the twine tails will end up in the entrails of life-stock, where they may cause digesting problems or even poisoning as a result of the chemical coloring agents contained therein. Some crops that are used for industrial processes must be prevented from being polluted with synthetic twine tails lest the harvested bale would be worthless and could not be used for further processing.
To attenuate the above disadvantages of the presence of twine tails, U.S. Pat. No. 4,805,391 discloses a system to collect the twine tails. A suction fan, connected on one side by hoses to intake units, and on the other side to a container, conveys twine tails from the knotters to the container. Such a collecting system suffers from the disadvantage that sometimes twine tails escape the action of the fan because insufficient suction power is available. The above described problems of twine tails ending up on the field or hampering the operation of the knotter system, thus still remain. Another disadvantage of this system is the necessity of providing an extra device that moreover needs to be powered to collect the twine tails. Since baler knotters are very complex devices, with a high number of elements rotating and moving in different planes, there is little or no space available for such a device in the area of the knotter.
Apart from double knotter systems forming two knots on a single loop, it has been known for many years how to close a loop around a finished bale with a single knot. The biggest disadvantage of a loop formed with one knot at the end of the baling process is that relatively high forces are applied to the twine when the bale is formed. Single knotter systems indeed require the twine to be pulled through the baling chamber and around the formed bale in order to be able to close the loop. The higher forces on the twine increase the danger of twine failure or the occurrence of misshapen knots.
On the other hand, single knotter systems have the advantage that various types of knotters may be employed, one of which being the conventional knotter already referred to in connection with the double knotter system and producing the twine tails as already explained. Moreover, another type of knotter suitable for a single knotter system is the so-called loop-knotter, producing a small loop on top of the knot. Since loop-knotters operate according to a tying principle which is different from conventional knotters, no twine tails are generated during formation of a knot. The positioning of a loop-knotter relative to the formed bale is such that the bale will pull the formed knot from the bill hook when the knot is made, cutting the formed knot loose from the remaining strand. The retained strand is then used for forming the next loop around the next forming bale.
To avoid the formation of twine tails, loop knotters unfortunately cannot readily replace the conventional knotters of a double knotter system, as the operating principle of a double knotter system cannot merely be regarded as a duplication of a single knotter system. When the two knots are formed with a conventional knotter, the bale in the baling chamber remains stationary. This means that no pulling action from the formed bale on the knot can be achieved. So pulling the knot from the bill hook as is done with a single loop-knotter is not possible.